In a switched-capacitor system, for example a switched-capacitor analog-to-digital converter, the input common mode is obtained, according to the prior art, by using a voltage generator generating the desired common-mode voltage, and by a set of two external resistors connected between the output of the generator and the differential inputs of the analog-to-digital converter. However, such an implementation suffers from a voltage drop at the external resistors because of the consumption of current at the input nodes of the analog-to-digital converter. This consumption originates from the leakage currents during the successive switchings of the switched-capacitor system and/or of the substrate current (“bulk”) in the transistors used as switches.
Because of this, the common-mode voltage at the inputs of the analog-to-digital converter may be significantly different from the desired common-mode voltage, this difference being able to be of the order of a few hundreds of millivolts.